There is often a need to put a spacer into an electronic device to provide a cavity. For instance, U.S. Pat. No. 4,113,360 describes an indicating device for displaying symbols. This device has a plate of fluorescent material which emits light, contained within a light guide. On this is placed a small electrode or other conducting material. Above this is placed a light dispersing material on a spacer such that at rest the dispersing material is held away from the light guides plates. Above the light dispersing material there is a transparent plate with an electrode pattern corresponding to the one on the light guide. By applying a voltage between the electrodes, the light dispersing material can be brought into contact with the light guide, decoupling the light and therefore illuminating the device. Whilst out of contact it remains unlit.
PCT Patent Application, WO 00/38163, describes an improved device whereby a complete display of pixels can be formed that can be addressed using column and row addressing. This structure is shown on a rigid glass support. The column plate has a conductor under a relief over which is stretched a translucent membrane. Above this is a row plate with conductors orthogonal to those on the column plate.
One way of making the relief structure over the top of the conductor is to lay down a light sensitive polymer on top of the device covering the conductors and underlying support and then to expose this to a mask identical or similar to the conductors. However, there are several problems associated with this. These include contacting, registration and differential expansion of the mask and the resist covered device. This can be overcome by putting the mask and device in a vacuum frame or by using careful clamping. Registration can be done laboriously by hand or by a specially designed robot. Differential expansion can be overcome by keeping the temperature and humidity of all components constant at all times. All these operations can be accomplished but at a high cost and time.
U.S. Pat. No. 5,707,785 discloses spacers for liquid crystal displays. It describes using an opaque mask laid down in the pattern of the relief but this has no conductive properties.